(HealthDay News) — Elderly patients with dementia and delirium who are taken to a hospital emergency department often do not comprehend why they are there and do not understand discharge instructions from doctors or nurses, a new study finds.

U.S. researchers interviewed 202 elderly patients about why they were in an emergency department and found that those with cognitive impairment (dementia and delirium) were less likely than those with no cognitive impairment to agree with the person who brought them to the emergency department about why they were there.

The study authors also interviewed 115 elderly patients about their discharge and found that those with cognitive impairment were much less likely than non-impaired patients to understand their discharge instructions.

The study results were published online Jan. 21 in the journal Annals of Emergency Medicine.

“Emergency physicians miss delirium and dementia in the majority of cases because emergency patients are not routinely screened for them. Our study suggests screening for these forms of cognitive impairment in the emergency department is warranted,” lead author Dr. Jin H. Han, of Vanderbilt University in Nashville, Tenn., said in a journal news release.

Dementia and delirium affect about 25 percent of elderly patients seen in emergency departments, according to the researchers. Communication problems with these patients “affects our ability to adequately provide quality care for these vulnerable patients,” Han said.

“We need to do a better job in identifying older patients with cognitive impairment, but this can be challenging in the chaotic emergency department environment. For this reason, we and several other research groups are trying to develop brief screening tools to help the busy emergency physician better identify delirium and dementia,” Han concluded.